First, a Supreme Court “stay” suspended the plan, pending court rulings on its legality, thereby clouding its long-term prospects. Days later, the death of conservative justice Antonin Scalia threw everything back up into the air.

Carbon Brief wraps up analysis of recent events and the implications for US efforts to address climate change.

Surprise stay

Last Tuesday, the Supreme Court issued a short, two-paragraph decision freezing the Clean Power Plan. The Environmental Protection Agency (EPA) will have to suspend implementation and states will be able to skip a September deadline for submitting compliance plans or asking for an extension.

The decision was “unprecedented”, said the New York Times, as the Supreme Court had never before granted a stay in similar circumstances. As the BBC noted, a DC Circuit Court had refused to issue a stay in January.

The battle over the Clean Power Plan now moves back to that DC Circuit Court, which agreed to consider the legal challenges at the same time as refusing to issue a stay, reported Vox. The lower court will hear oral arguments on 2 June and could make a decision by the autumn.

The surprise stay erodes a key strength of the plan, which was supposed to generate its own momentum even as the legal back-and-forth continued.

In a Supreme Court decision last year, the EPA lost a case over its mercury regulations, yet the ruling, ultimately, had little impact because power companies had already largely implemented its requirements, as Vox explained.

Janet McCabe, the senior EPA official with responsibility for the Clean Power Plan’s implementation, told Carbon Brief in December that utilities saw the plan “as an opportunity”. She said almost all states were drawing up compliance plans, even if they were opposed to the rules.

As a result of the stay, some states say they will now suspend action, reported ClimateWire, though others will continue to plan for it eventually becoming law. Legal issues may slow, but not stop state carbon-cutting efforts, it reported.

For many electric utilities, the decision “doesn’t really change anything”, EnergyWire said. In a similar vein, the Washington Post argued the move to clean power is “proceeding, regardless” of the legal wrangles. A second article said the courts “can’t stop clean energy”.

Obama told supporters not to “despair”, reported the Hill. White House officials dismissed the “procedural” decision as a “bump in the road”, reported the Financial Times and the Guardian.

International reaction to the news was mostly tentative, despite a Wired headline claiming that the decision “may have nuked the Paris climate deal”. Politicians, businesses and campaigners from other countries “rallied to support” Obama, reported the Guardian.

If the Clean Power Plan is ultimately ruled illegal, however, the chance of nurturing trust between countries would all but vanish, one Indian analyst told the New York Times.

Sudden death

A more gloomy analysis of the Supreme Court ruling was that it augured badly for the Clean Power Plan’s ultimate fate. The decision had split the nine justices 5-4 along partisan lines, said Reuters, with all five conservatives voting to stay the plan and the four liberals dissenting.

With the split likely to be repeated in later rulings on the plan, the decision was an early hint that it would face a tough ride from the justices further down the road, said the New York Times.

That calculus was thrown into uncertainty on Friday after the sudden death of 79-year-old justice Antonin Scalia. The National Law Journal says he was “leader of the court’s conservative wing”.

Scalia’s death will “likely spur a tectonic shift in environmental law”, says Greenwire. Scalia did not believe carbon was an “environmental pollutant”, notes Andy Revkin’s Dot Earth blog. Instead, Scalia said carbon was an atmospheric pollutant, arguing the EPA had no authority to regulate the atmosphere. That’s why he dissented in 2007, when the Supreme Court ruled that the EPA had authority to regulate CO2.

Scalia had also authored the 5-4 majority finding against the EPA in last year’s mercury ruling. In criticising the EPA’s approach, Scalia had signalled a shift away from a doctrine that courts should defer to any reasonable interpretation of the law made by federal agencies.

With Scalia’s passing, the Supreme Court is left with eight justices split evenly between conservatives and liberals. We’ll look at what this split means in a moment.

In terms of filling that ninth seat, President Obama is constitutionally obliged to propose a replacement. His nominee must be approved by the Republican-controlled Senate, however.

Republican presidential hopefuls have been quick to argue the next president should choose Scalia’s replacement, reports Greenwire. For instance, Donald Trump called for “delay, delay, delay”, says the New York Times Magazine, foretelling the “next frontier in political hardball”.

The Senate has refused to act on a Supreme Court nomination in a presidential election year at least once before, notes the Washington Post. It recounts how it has become increasingly difficult to confirm any judicial nominees during an election year.

Even so, most presidential nominees are, ultimately, accepted by the Senate, reports Greenwire, noting that a delay would be unusual. It says the average gap between nomination and a Senate vote is 67 days, with 341 days of Obama’s presidency remaining.

Political nominee

The politics of the nomination are complex, SCOTUS Blog explains. Obama could choose a moderate candidate, hoping to secure the Republican votes he needs, says Reuters. Alternatively, a strong liberal choice might reap political capital from the Senate’s likely refusal.

Hillary Clinton says Republican opposition to any Obama nominee is “outrageous”, reports the New York Times. Either way, the Supreme Court is quickly becoming a campaign issue.

The search for likely nominees is already underway. Politico has a shortlist, as does the National Law Journal. DC Circuit Court judge Sri Srinivasan — described as a “nominee in waiting” by a 2013 New Yorker article — tops several of the lists. SCOTUS blog argues a female nominee, such as attorney general Loretta Lynch, is more likely.

Srinivasan’s court is due to hear the Clean Power Plan case and he might have to recuse himself if nominated, potentially complicating the outcome, Greenwire says. Apart from this small wrinkle, however, the DC Circuit Court is expected to uphold the Clean Power Plan, reports Vox.

If that happens, the Supreme Court would have to decide whether to make its own ruling on the Clean Power Plan. If Scalia’s replacement is delayed and the Supreme Court splits 4-4, then the ruling of the lower DC court is automatically affirmed.

This means Scalia’s death has significantly boosted the chances of the Clean Power Plan coming into force, reports Bustle, with several other outlets carrying similar arguments.

Election year

The change in Supreme Court make-up will, of course, have far-reaching impacts in other areas of US law, from race and immigration through to gun control and abortion, report the New York Times and the Guardian.

While much remains to be decided, last week’s events for the Supreme Court highlight how pivotal the presidential election will be for US climate efforts and beyond: at least three other justices are likely to be appointed over the next two presidencies, says the Election Law Blog.

If a Democrat enters the White House in 2017, a liberal Supreme Court majority and continued climate action is all but assured. If it’s a Republican, the opposite applies in spades.